The present invention involves a novel design for an improved centrifugal collet adapted for use in a high speed drilling or machining apparatus, the like of which may be utilized in a commercial printed circuit board (PCB) drilling unit. It greatly increases the gripping power and the accuracy of the centering of the tool bit held within the collet as well as allowing for quicker tool bit changes.
Commercial PCB fabrication requires the drilling of numerous holes often in the micron range and at very specific spacing's and depths. The accuracy of this is dependant on the precise centered placement of the drill bit within the collet. The drilling is done in rapid succession, generally with numerous z-axis drilling assemblies affixed to a single moving arm and at drilling cycles lasting a fraction of a second each. The drill bits used dull and need to be replaced on a frequent basis. Time lost in changing the tool in the collet reduces production. Prior art collets for high speed commercial production drilling or machining apparatuses utilize numerous parts and generally are of the air actuated, spring loaded tapered collet design. These have several drawbacks. With many parts moveable, during operation it is it is easy for parts to shift their locations slightly. This creates a problem as the collet can get out of balance. In high speed rotation (up to 400,00 RPM) this can have disastrous, self destructing effects to the collet and spindle. With increasing RPM on the traditional taper style collet, the grip on the tool bit relaxes.
Henceforth, a centrifugal collet for holding machine tools (such as a drill bit) in a high speed drilling or machining apparatus with decreased runout and increased gripping force that is capable of faster changeout times would allow for, faster and deeper drilling (increased PCB substrate stack heights), longer drill bit life, less drill bit breakage and a higher machine throughput. This would fulfill a long felt need in the substrate drilling and surface patterning industry. This new invention utilizes a unitary centrifugal collet that combines known and new technologies in a unique and novel configuration to overcome the aforementioned problems of the prior art PCB drilling systems.